No. 6 (2020)

This paper considers infrastructure to wireless mobile communications using Advanced-WiMAX. In this paper, the productivity performance throughput experienced the mobile users is compared in the cases of 3D SISO and 3D MIMO-channel models within a large urban cell. Re-cently, there has been substantial work and interest to expand MIMO and SISO-processing by taking into consideration in the design the elevation plane in addition to the azimuth dimension, Since the evaluation of elevation MIMO and SISO performance in 3D-channel design is needed. Bit-level simulation is performed for the channel in WiMAX operating at 2.5 GHz. The results indicate the accuracy of the 3D channel model, and the correct estimation of the 3D channel is showed. The difference in higher predicted capacity for the 3D channel model has resulted in the small-scale parameters for the SISO-case and the lower spatial correlation parameters for the MIMO-case. Different mobility speeds, the effect of the Doppler shift, several paths and the signal attenuation at a distance and with increasing frequency has been carried out in this study. Simulation runtimes are measured concerning the multi-section modulation types for both systems SISO and MIMO. Noise immunity is adversely affected by an increase in the number of spatial streams. The noise immunity is also affected by the increase in the number of antennas at the transmitters and receivers.

The physical principles of the hydroacoustic wavegraph’s operation, which is the facility for
measuring of hydro conditions on the seadrome’s aviation water area, are considered. The device
includes channels for both measuring the parameters of sea waves in the wave recorder mode by
the "inverted" echo sounder method and processing Doppler information to search for the general
direction of propagation of the surface wind wave due to oblique echo sounding of the agitated
interface from the bottom of the water area. A distinctive feature of the wave recorder is the use of
a bottom receiving-emitting antenna assembly of an original design, which allows the simultaneous
operation of both channels, moreover, on several working ultrasonic signals due to the use of
nonlinear acoustics effects - self-action and self-demodulation. For example, due to the effect of
self-action, the spectrum of the probing signal with a frequency is "enriched" with higher harmonic
components with frequencies, where is the number of harmonics for which ultrasonic fields have
features - the angular width of the main lobe of the directivity characteristic in the radiation mode
for each subsequent harmonic is less, and the level of the side field - below. The device can provide
registration of sea waves parameters (direction of wave movement, height and wavelength,
wave period) for a long time with high accuracy, reliability and stability, which makes it promising
for use as part of reference systems.

This article discusses the issues of increasing the noise immunity of semi-active radar systems
based on the use of transmitters for target illumination using harmonic radiation and remote
Doppler receivers in conjunction with a central information processing station. This solution is
not only the simplest from the point of view of hardware implementation, but also has such advantages
as high speed and increased sensitivity, as well as the ability to search-free spatial and
frequency processing of radiation. Of the shortcomings, it should be noted the low secrecy of the
functioning of this semi-active radar system. The purpose of the work is to eliminate the indicated
drawback by using frequency tuning in the illumination transmitter or when using several spaceseparated
illumination transmitters operating according to a given frequency-time scheme in a
semi-active radio-location system. In addition, the paper deals with the optimization of the main
parameters of portable Doppler receivers of semi-active radar systems. In particular, the paper
gives recommendations for reducing the blinding effect of a direct signal to a Doppler receiver
and presents a set of measures aimed at increasing the range of action of semi-active radar systems
up to forty kilometers. In this paper, we consider the case of operation of a semi-active radiolocation
system operating in a limited spatial sector using one remote receiving point. The illumination
transmitter, which is usually placed on a high-rise object, generates directional radiation,
intended primarily for solving various tasks in the field of telecommunications, for example,
providing mobile communications, relaying satellite information, etc. In this system, the illumination
transmitter is used in as a signal generator for illumination of air targets

The problem of forming a radar image (RI) of the earth's surface in real time remains one of
the most urgent in solving radio imaging problems, despite the appearance of a large number of
publications in this area, reflecting a whole range of new methods and algorithms for processing
trajectory signals in order to improve the quality of images. The main goal in the formation of
radar images is to achieve the maximum resolution and image quality under real constraints associated
with the drift of the parameters of the received trajectory signal (synthesis time), measurement
inaccuracy and variability of flight characteristics (speed, acceleration, flight trajectory),
exposure to a wide range of noise and interference, both external and internal, against the background
of a low-power received signal from remote radio reflectors (energy resources). The article
investigates an algorithm for constructing and restoring images of the underlying surface and
develops its software implementation. The effectiveness of the new approach is shown using several examples for various areas of the underlying surface with a blind spot. The subject of the research
is methods and algorithms for constructing a terrain map and reconstructing lost image
areas. The research object is a set of test images. The result of the research is the development of a
method for image restoration in order to restore the lost area. The novelty of the work is an algorithm
that improves the quality of image restoration based on a neural network. The results obtained
make it possible to restore the areas. Evaluation of the efficiency of the image restoration
method was carried out using a statistical criterion - the root mean square error of the processing
result from the true image. As a result of solving the tasks, we can draw conclusions:  A method
was developed for constructing and restoring images of the underlying surface based on the
search for similar blocks with their subsequent combining by a neural network.  Analysis of the
results of the study showed that the proposed method improves the quality of image reconstruction.

The paper considers the development of technologies for integrated high-precision navigation
of unmanned amphibian aircraft (UAA) to ensure both positioning and navigation on the surface in
conditions of limited atmospheric visibility (low cloudiness, masking effect of hydrometeors, night
time, etc.) in the seadrome’s water area using hydroacoustic a remote control channel operating
through the use of a bottom network structure of original transmitter-receiver antenna assemblies
(TAA). Each individual TAA is proposed to be used as an "omnidirectional" sonar bottom beacon in
the upper hemisphere, consisting of electroacoustic transducers (ET), each of which operates in the
mode of the parametric transmitting array. The statically generated "partial" lobes of the resulting
DP of single TAA are uniformly quantized over the bodily sectors in the hemisphere; moreover, due
to the use of nonlinear acoustics effects, an individual "frequency coloration" of each of the bodily
sectors is possible. As a result, an individual distribution of “frequency-colored spots” of local ultrasonic
irradiation can be formed at the “water - air” interface of a given section of the aviation water
area, and, both continuous and discrete, the latter can be considered as separate points of the required
trajectory of the UAA, radio electronic equipment which tracks the "acoustically marked"
section of the required direction of the wiring located ahead of the course.

In the modern world, one of the important communication channels is the Internet. Trade,
promotion of services is carried out through electronic platforms. Social networks and instant
messengers are becoming the most important communication channel and a powerful tool for
influencing public opinion. A significant amount in all published content falls on texts written in
natural language. Therefore, the problems of natural language processing (NLP) and natural
language understanding (NLU) today are one of the key ones. Under the influence of commercial
interests, the field of automatic aspect-based sentiment analysis is actively developing. This task
significantly depends on specific subject areas, and therefore the issue of quick and effective adaptation
of existing models to new domains is very acute. The paper proposes a hybrid method of
aspect-oriented analysis, based on data extracted from common dictionaries and domain-oriented
texts. The novel method for constructing a condensed semantic graph based on unstructured domain-
dependent texts is proposed. Numerical metrics to assess the significance of individual termswithin the entire domain are introduced. An algorithm for the text categorization based on the
selection of semantic clusters within a condensed domain-specific graph is proposed. A method for
assessing the sentiment of domain-oriented texts based on statistical data, including the joint use
of a tone lexicon and a condensed domain-specialized graph, is proposed. The results of experiments
are presented, allowing for evaluation of the quality of the algorithms.

The article is devoted to the assessment of the influence of magnetic interference, in the
study of thermal fluctuation processes in the dynamic current load mode of a power cable line
(SCL). On the basis of such artificial intelligence methods as neural networks and fuzzy logic, the
thermal resistance of SCL insulating materials determining the throughput of the cable line of
electric power systems was investigated. A comparative review of the currently existing traditional
non-destructive methods for predicting thermal processes in SCR showed that most of the methods
have a low prediction accuracy, as well as have a high degree of complexity and a large number
of necessary computational operations to obtain the necessary data for predicting thermal processes
in SCR. Also, most forecasting methods are not able to work in real time, which is an extremely
significant drawback. To solve this problem, it is necessary to resort to forecasting systems
that are based on artificial intelligence using machine learning methods. The method of artificial neural networks (ANN) seems to be the most promising today. The need to develop a more
perfect method for analyzing the aging of SCR insulating materials is shown. The urgency of the
problem of creating neural networks (NN) for assessing the throughput, calculating and predicting
the temperature of SCL cores in real time based on the data of the temperature monitoring system,
taking into account the change in the current load of the line and the external conditions of heat
removal, has been substantiated. A neural network has been developed to determine the temperature
regime of the current-carrying conductor of a power cable. A comparative analysis of the
experimental and calculated characteristics of temperature distributions was carried out, while
various load operating modes and functions of changing the cable current were investigated. A
neural network model was developed in Matlab Simulink for predicting the temperature of a cable
core. The creation, training and modeling of the neural network was carried out using the Neural
Network Toolbox. The model can be used in devices and systems for continuous diagnostics of
power cables by temperature conditions.

This article proposes approach to the stability analysis in the sense of Lyapunov for systems
of ordinary differential equations. The approach is based on stability criteria in the form of necessary
and sufficient conditions obtained on the basis of matrix multiplicative transformations of
difference schemes of numerical integration. The matrix, multiplicative form of criteria implies the
possibility of their cyclic program implementation in the form of a cycle by the number of multipliers.
It is mathematically proved that the replacement of an infinite matrix product with a finite
product, which is necessary in the programming process, preserves the certainty of the stability
analysis according to the proposed criteria. The dependence of the certainty of computer stability
analysis on the error of the difference solution of a system of ordinary differential equations is
investigated. In order to improve the accuracy of difference approximations of the solution and
linearization of the system, the method of variable piecewise polynomial approximation of the
solution is used. The method gives continuous and continuously differentiable approximations of
the desired solutions over the entire integration interval. The required approximations are obtained
on the basis of a piecewise-polynomial approximation by Newtonian interpolation polynomials
converted to the form of a polynomial with numerical coefficients. Computer approximation
of integrands increases the accuracy of integral calculation. This increases the accuracy of calculating
expressions in each multiplier of matrix products, and consequently increases the certainty
of analysis using stability criteria. A program and numerical experiment was conducted to analyze
the stability of the Lorentz system under given initial conditions and parameters changes. Based
on the numerical data obtained during the experiment, the stability nature of the system under
study is unambiguously established. In General, the proposed approach makes it possible to perform
a stability analysis arbitrary systems of ordinary differential equations in real time mode
without access to methods of the qualitative theory of differential equations and systems of computer
mathematics.

The paper proposes a modified distributed data processing architecture based on the clientserver
model, as one of the options for implementing a software application of a geographic information
system. The review of existing geographic information systems and their classification
from the point of view of architecture demonstrated the prospect of using a distributed architecture.
However, systems developed on the basis of a traditional distributed architecture face problems
displaying processed 3-dimensional data in real time on computing devices with low performance.
In this regard, the purpose of this work is to develop and study a modified architecture of
geographic information systems, which allows to reduce the requirements for computing devices of
clients. The relevance of the research topic lies in the fact that currently there are devices that can
support only thin clients, which often have small functionality and are not able to solve heavy
computing tasks. The article discusses the features of the structural and software implementation
of a geographic information system based on the traditional architecture and the proposed modified
distributed architecture. The results of experiments carried out on two developed software
applications with different architectures are presented. The software implementation of the modified
architecture and the results of experiments have shown the feasibility of its application for
geographic information system systems on user computing devices with low performance.
The proposed architecture can be used in other distributed systems as well. Especially in those
where the task is to display three-dimensional information on thin clients.

Effective protection of information in an information system implies regular diagnostics and
monitoring of the network, computers, and applications to detect possible problems in the security
system. There are vulnerability scanners certified by the Federal Service for Technical and Export
Control for security scanning. As a result of scanning, vulnerabilities of the information system
can be identified, the elimination of which requires an immediate response, since attackers can
take advantage of the vulnerability of the information system and carry out an attack. However,
the selection of protection measures is a laborious process and requires a large amount of time,
then the problem of automating the selection of information protection measures arises. The development
of an algorithm for the automatic selection of information security measures is the main
goal in automating the work process of an information security specialist. The main tasks in the
development of the algorithm: selection of the fundamental characteristics of the vulnerability,
generation of a list of protection measures taking into account the security class of the information
system, comparison of protection measures with the selected characteristic. After analyzing the
information about vulnerabilities, the main indicator is chosen the vulnerability vector, which
includes the main metrics, the assessment of which allows the choice of protection measures. A set
of information protection measures was compared to each metric by means of expert assessment.
During the operation of the algorithm, the employee sets the vulnerability vector and the security
class of the information system as input parameters and as a result receives a list of necessary
protection measures. Thus, the automatic selection algorithm assumes a comparison of vulnerability
metrics with information protection measures, which will allow an employee to quickly select
measures based on the identified vulnerabilities.

Network traffic analysis allows you to solve many problems, such as: determining the pattern
of data transmission over the network, collecting statistics on the use of web applications,
monitoring and further researching network load, identifying potential malicious software and
network attacks, etc. 40% of Internet traffic belongs to unknown applications. This suggests that
for the area of network traffic analysis, the task of classifying applications has acquired particular
importance. Improvements in software in the field of network technologies have contributed to the
discovery of serious vulnerabilities in the implementation of some network protocols, namely TCP
and HTTP. By using network traffic analyzers, an attacker gained access to the contents of data
packets transmitted over the network. However, with the increasing qualifications of the information
community in the field of computer security, as well as with the development of network
technology standards, the analysis of network traffic has become noticeably more complicated.
The increased use of mathematical methods for protecting information, such as symmetric and
asymmetric cryptographic protocols, has led to the fact that most approaches to the analysis of
network traffic have lost their meaning and are no longer used. Therefore, the search for new
solutions to the problem of classifying network traffic, taking into account the possibility of its
encryption, is relevant. The article is devoted to the description of a new mixed approach to the
analysis of network traffic, based on the combined use of information theory and machine learning
algorithms. It also provides a comparative analysis of the proposed method with existing approaches
based on both information theory and machine learning. The aim of the research is to
develop an algorithm based on an intelligent approach to the analysis of network traffic. The proposed
algorithm is based on calculating entropy and using neural network classifiers. Research
objectives include: theoretical substantiation of the proposed approach in the field of information
theory, as well as machine learning algorithms; carrying out a structural description of the implemented
algorithms for calculating entropy and classifying applications that generate encrypted
traffic; comparative analysis of the proposed algorithm with existing approaches to the analysis of
encrypted network traffic. The result of the research is a new algorithm that allows classifying
various types of encrypted traffic with a high degree of reliability.

Mathematical model of multilayered printed frequency selective surfaces with dielectric covers
is presented in this paper. The model is built on the suggestion of array infinity and perfect
conductivity of microstrip elements. Such printed structures can be used as frequency selective
surface and as covers with controllable characteristics (for example tunable filters, adaptive radar
cover, electronically switched polarizers). Full-wave analysis is executed by the integral equation
method. The numerical solution of an integral equation has been obtained by Galerkin’s method.
Unknown distribution of surface magnetic currents has been approximated by roof-top basic functions.
The generalized scattering matrix method was used for simulation of multilayered printed
frequency selective surface. The paper presents the compound algorithm which combines the integral
equation method with the method of generalized scattering matrix. A lot of numerical examples
are presented proving the algorithm effectiveness. By means of this model there were synthesized
multilayer frequency selective surface as periodic arrays of the printed elements, which have
arbitrary shape of reradiators. It is known, that the printed elements of special shape ensure, as
rejecting and as transacting of electromagnetic waves in the given frequencies, and have neglected
angular sensitivity. The results of constructive synthesis of printed frequency selective surfaces as
rejecting or transmitting filters, which have neglected angular sensitivity, are represented in paper.
Such an algorithm is rather flexible and multiple repeats the basic problem solution. It makes
the procedure of computer code preparing much more effective and do not require to change the
problem decision itself.

At all stages of the development of information technology, much attention has been paid to
the issues of modeling functioning specialized high-performance computing systems, which make it
possible to provide the necessary performance indicators in combination with minimized costs of
software resources and energy consumption. The developed information system, focused on human-
machine interaction, allows you to clearly see the strengths and weaknesses of the developed
quantum computing device, to prove the advantages of its use. The developed modeling information
system is a visual aid for understanding the main methods of interaction between information
processes and information resources. A number of the most important problems cannot be
solved using classical computers, including classical supercomputers, in a reasonable time. Recently,
there has been a surge in interest in quantum computers. This article is devoted to solving
the problem of research and development of a circuit and a simulation technique for a hardware
accelerator of quantum computing. The work touches upon the problems of research and development of methods for the functioning of quantum circuits and models of quantum computing devices.
The relevance of these studies lies in the mathematical and software modeling and implementation
of the fundamental components of quantum computing models. The scientific novelty of
this direction is expressed in the optimization of the quantum computational process. The scientific
novelty of this area is primarily expressed in the constant updating and supplementing of the field
of quantum research in a number of areas. The aim of this work is to implement a technique for
constructing a hardware accelerator. The technical support of the information quantum system
and processes has been implemented, including new software for the transmission and presentation
of information. The use of a quantum computing information system differs from its counterparts
by a significant increase in the speed of solving computational problems and, most importantly,
by an exponential increase in the speed of solving NP-complete problems that can be
solved on classical machines in unacceptable time. Due to the fact that the class of NP problems is
wide, the applicability and significance of the developed method for constructing a modular system
of quantum computing is beyond doubt.

This article discusses the problems of ensuring the flight safety of aircraft using electrical /
electronic systems when exposed to high-intensity electromagnetic fields. A method is being developed
for analyzing the impact of high-intensity radiated fields that create an electromagnetic environment
in the aircraft location area, based on the main factors of the aircraft electromagnetic
compatibility, such as the electromagnetic environment, the mechanism of communication or action,
the sensitivity or susceptibility of electromagnetic radiation receivers with threshold values of
interference in the frequency and time domains. Two methods for assessing the aircraft resistance
to high-intensity electromagnetic fields are analyzed: high-level scan tests and low-level scan
tests. The purpose of this article is to estimate the fuselage shielding coefficient in the places
where critical systems units are installed using software for numerical electrodynamic modeling.
The objective of the study is to create and calculate a mathematical model of the critical system as
part of an aircraft. The article developed electrodynamic models of the critical system of the aircraft
– a multifunctional liquid crystal indicator, and the calculation is carried out in the Ansys
HFSS full-wave electrodynamic design package. Reasonable simplifications are made to the HFSS
cockpit model for calculating the fuselage-shielding factor. Simplifying the model means eliminating
small parts and objects that are much shorter than the wavelength and reducing the model's
area of study, since the critical system blocks are located in the front of the cockpit. The estimation
of the fuselage-shielding factor in the frequency range from 100 MHz to 1 GHz is carried out, the
analysis and comparison of the results obtained with the tests in the aircraft are carried out. The
results are of a similar nature, however, the calculated values of the shielding factor are 5–15 dB
lower in the frequency range from 400 to 850 MHz. Also in the frequency range up to 400 MHz,
there are characteristic resonant "dips" of the screening coefficient. The results obtained will
make it possible to single out the most dangerous sources and zones of excitation of electromagnetic
interference for subsequent detailed analysis, and to reduce the time and cost of testing.

Methods of functional electronics, particularly acousto-optical (AO) method of radiosignal
processing, strongly lead even in comparison with DSP in cases requiring in minimum time period
in wide analysis band with high accuracy to measure frequency and time parameters of several
simultaneous signals. Development of new technologies and materials makes using the AO devices
more actual since, according to integral features (consumption power, sizes, mass), they take leading
places among other radiosignal parameters measurers types. AO cymometers as a kind of AO
measurers take their firm place in an equipment of radiosignals parameters evaluation due to
unique characteristics – multisignal mode, resolution, small sizes, acceptable input dynamic range
and frequency evaluation accuracy. These devices are capable to practically instantly translate
signals from time to frequency domain and find application in systems of passive radiocontrol
where important parameters are not only dynamic range, evaluation accuracy of frequency and
phase, but also energy consumption, mass and sizes that become considerable in mobile and space
measurement complexes. By this reason in many countries AO cymometers have been successfully
utilized in air and space engineering. Technical parameters of AO cymometers, such as band,
nonuniformity of working channel, AO interaction efficiency etc. are largely defined by parameters of
AOD (AO deflectors). Among all elements of AO device AOD are more expensive and together with
lasers and photoreceivers AOD manufacturing also requires high technologies applying. Along with
development and production not less important and technically complicated (that influences the AOD
cost) is the task of development of ways computation, control and measurement of OD parameters.
This work authors, being coworkers of laboratory "Nanophotonics and optoelectronics" of SFedU,
have solved the task of calculation of technical and technological parameters of AOD of two frequency
bands, have developed documentation, that allowed to manufacture several AOD samples, have
developed the system of testing, that have been carried out, and implemented the correction of AOD
electrodynamical structure parameters. Given are the parameters calculation and math modeling
AOD electrodynamical structure, the method of measuring the AOD parameters, the layout of
testing set. Also given the results of experimental investigations of developed AOD. Shown that
electrodynamical structure correction allows in constrained range to change the AOD parameters
and only adjusting capacitor does not allow to match parameters, but it is necessary to execute the
matching system topology correction. Theoretical calculations and modeling have been confirmed
by experimental results of manufactured AOD.

This article is devoted to PZT-based solid solutions as the basis of active elements for
single-use pulsed energy sources. The article evaluates the generating ability of a
piezoceramic material based on lead zirconate-titanate with a low titanium content
(Zr/Ti 0,94/0,06 + 1 % Nb2O5) under its shock loading. In such materials, the pressureinduced
(uniaxial, pulsed hydrostatic, or shock wave) phase transition occurs from the polar
ferroelectric phase to the non-polar antiferroelectric phase. The released energy in this case
is an order of magnitude higher than with the piezoelectric effect. A measure of the accumulation
of electrical charge is the value of the residual polarization, which is proportional to
the electrical energy released during the phase transition. In the course of the work, the main
electrophysical parameters of the material under study were obtained: relative dielectric
constant, dielectric loss tangent in weak fields, piezoelectric charge constant . A number
of numerical values of the residual polarization of the material under study were obtained by
several methods: thermal depolarization and shock loading; the accumulated energy density
is calculated as the ratio of the residual polarization to two absolute dielectric constants. An
assessment of the generating capacity of the material under study and a comparative analysis
with the industrially produced piezoceramic material PZT-19 are carried out. It was found
that the density of the accumulated energy of the material under study is two orders of magnitude
higher than that of PZT-19. It is also worth noting that the pressure-induced phase transition
from the ferroelectric to antiferroelectric phase for materials with a low titanium content
occurs at much lower pressures than in materials located near the morphotropic boundary.
This behavior is due to the fact that the energies of the states of the ferroelectric and
antiferroelectric phases differ insignificantly; therefore, a relatively small external influence
(pressure or electric field) is sufficient to violate the existing stability and transfer
piezoceramics from one phase state to another. This fact has a positive effect on the generating
ability of elements made of the material under study, since when exposed to high pre ssure,
the electrical resistance of the piezoelectric ceramics decreases significantly, and a
significant part of the electrical energy can be dissipated in the piezoelectric element itself.

In this article additional temperature error of vibration density meters in liquids and gases
is reviewed. Particularly scrutinized are the effects of change in the temperature of the medium
on the vibration frequency of the density vibration transducers. Main principle of operation
and advantages of vibration density meters is described. The article analyzes and describes the
existing algorithms of calculating density and active temperature compensation as well as the
disadvantages of those algorithms. It points out to the significant limitations of temperature
calibration diapason of the existing methods which relate to the necessity of using distilled water.
Basing on the previous vibration transducer simulation and on the established main function of the elastic modules of the metal’ temperature properties a new thermal compensation
algorithm, which does not involve liquid compensators, was introduced. Main advantages of the
new algorithm are demonstrated. Those advantages emerge due to using vacuum as a medium
surrounding the vibration transducer. One of the most notable benefits is significant extension
of the calibrated temperature range. A possibility of applying the algorithm for calibrating density
meters in extreme temperatures is introduced. Furthermore, formulas for calculatingthe
value of the oscillation period of the converter which account for temperature changes (thermal
compensation period) are presented. The advantages of using second order polynomial with
zero linear term as a calibration function are also provided. Methodology behind conducting
the experiments, types of equipment and measuring instruments are described in detail. Resul ting
experimental data for vibration transducers made of three different metals is presented. The
obtained data is analyzed, which led to a conclusion that application of suggested algorithm of
thermal compensation of liquid and gases density meters’ vibration transducers is feasible and
expedient.

Heterodynes are an integral part of any superheterodyne receiver. They determine the stability
and accuracy of the receiver settings. The purpose of this work is to create a heterodyne
module with improved electrical parameters, with small dimensions and weight. The object of
research is a five-channel heterodyne of the centimeter wave range. Such a heterodyne can be
used in a multi-channel superheterodyne signal detection receiver. An experimental study of two
five-channel channels-the upper and lower frequency heterodyne tuning. The results are presented
in the form of frequency run-out curves for half an hour of operation after switching on, as well as
the spectra of output signals in the near and far zones. The functional diagram of the module, a
brief description of the design and the experimental method are given. The design of the module
has the overall dimensions of the case 170x20x40 mm, is standardized and allows you to integrate
the module into various receivers. Each channel of the heterodyne module includes a voltage stabilizer,
an autogenerator with a dielectric resonator, a power amplifier and a power control detector,
and a power divider by two. As a result of the experiments, the following parameters were
achieved: – operating frequencies of 9.25 and 16.25 GHz; – maximum output power in the absence
of an amplifier of at least 2 mW; – the run-out frequency of 80 kHz to 9,25 GHz frequency;
– run-on frequency 600 kHz for the frequency of 16.25 GHz; – supply voltage + 15 V; – spectral
line width no more than 5 kHz; –second harmonic suppression of at least 25 dB; – there is an
on / off switch for each channel of the heterodyne module and built-in health monitoring.

Microelectromechanical sensors of the membrane type are fabricated by surface and bulk
micromachining. In the latter case, the membranes are obtained by deep anisotropic etching of a
single-crystal silicon layer or substrate to a thickness of 20–50 μm. In this case, both dry and wet
etching methods are used. The advantage of wet etching is easy control of the lateral dimensions
of the membranes and high selectivity. High selectivity of etching can be achieved due to the
choice of the appropriate composition of the etching solution, the material of the protective coating
and fabrication techniques. The paper presents an experimental study of the protective properties
of silicon oxide films obtained by thermal oxidation, plasma-chemical deposition, and combined
coating of these films under wet etching of single-crystal silicon in a 30% aqueous solution
of potassium hydroxide at a temperature of 80°C. The etching selectivity, residual thickness,
roughness, and surface concentration of local defects were calculated using data of stylus
profilometry, optical interferometry, and microscopy. It was found that the rates and selectivity of
etching of thermal oxide and plasma chemical oxide after rapid thermal annealing are quite close
– 6,7 nm/min, 1:338 and 7 nm/min, 1:372, respectively. The surface roughness of the oxide films
increased more when etching the thermal oxide films, as well as the plasma oxide of composite
coating. The root-mean-square values of the residual roughness were 1–2 nm. Local defects of the
etched alike with a concentration of 0,1–0,2 mm-2 were found in the films. It was found that the use
of a 1 μm plasma oxide layer in a combined coating prevents etching of the thermal oxide, but to
avoid local defects, its thickness should be increased to 1,5–2,0 μm; an annealed film of plasma
oxide, with a thickness of 2,0 μm, can also be considered as an effective protective coating for
deep wet etching of silicon.

the ingot internal uniformity, which is mainly determined by the initial solidification processes.
The imperfection of the casting process control at the initial section "ladle-tundish-mold", especially
the mold level, leads to occurrence of internal nonuniformity and surface defects, as well
as distortion of the slab shape. Thus, the level drop below setting value leads to inner surface oxidation
of the formed ingot crust and its structural nonuniformity. If metal level increases, overflow
over the ingot crust occurs, which leads to increase the oscillation traces depth and capture of
non-metallic and slag inclusions. Therefore, the mold is the most important technological element
of the continuous casting machine (CCM). The scientific and technical complexity of the mold
level control problem is the lack of technical capability of the metal level measuring in real technological
conditions with the required accuracy, as well as changes in the object parameters during
operation and in non-stationary modes. The modernization of existing control systems through
the introduction of new control algorithms is one of the ways to improve the efficiency of the metal
level stabilization control in the continuous casting machine mold. It demands to single out the
factors affecting the metal level stability in order to observe and compensate them. In this paper
implementation of the combined control principle based on the main disturbances compensation
and controlled coordinate feedback is proposed. The synthesis of static compensators with constant and variable compensation coefficients was carried out in accordance with the principle of
invariance, which allows to significantly reduce the deviation of the controlled variable in nonstationary
operating modes.

This study performed at the intersection of two areas: engineering and biomedical, which
resulted in the development of a therapeutic focusing ultrasound transducer designed for the detection
and non-invasive treatment of neoplasms. Main principle is emitting high-intensity ultrasonic
vibrations into the focus spot (High Intensity Focused Ultrasound – HIFU). This allows to
target selected areas and perform ablation of inflamed or foreign tissues without open surgery.
Based on the characteristics of piezoceramic materials produced in the "Piezopribor" SCTB,
mathematical modeling of the HIFU converter was performed. The basis is a piezoceramic element
made in the form of a thin-walled segment of a sphere with a central hole, made of ferroelectric
material PCP-35. The central hole with a diameter of 41.4 mm is designed for the imaging
sensor, which acts as a" gunner" of a focused ultrasonic beam. The principle of operation of the
transducer is as follows: the focal spot with the maximum acoustic pressure is located in the area
captured by the ultrasound-compatible sensor. The image is transmitted to the monitor, after
which a decision is made on which areas and with what intensity to influence the ultrasonic transducer.
The amplitude-frequency characteristics of the converter are studied. The dependences of
the active conductivity on the frequency in the free and water-loaded states are obtained. Acoustic
pressure levels in the focus spot were measured. Diagrams of the radiation intensity distribution in
the plane and in three-dimensional space were constructed, and work was carried out on the effect
of an ultrasonic transducer on various organic materials and tissues: organic glass with a thickness
of 10 mm, chicken muscle tissue. The dependences of the impact force on the power supplied
to the converter, as well as the frequency of the master signal, are obtained. The possibility of
using the converter as part of the HIFU therapy complex is experimentally shown. Conclusions
about the prospects of using single-element focusing ultrasonic transducers and multi-element
ones with a distributed focus spot are formulated.